Self-encoding keyboard employing eddy current shorting

ABSTRACT

A self-encoding keyboard which employs eddy current shorting effects for generating coded digital electrical signals representative of actuated keys. Each key includes a metal element which upon actuation of the key is brought into close proximity to a corresponding group of stacked printed circuit windings so as to produce an eddy current shorting effect which is detected and used to produce a group of coded digital output signals uniquely representative of the actuated key. Winding encoding arrangements employing two windings per binary digit as well as a single winding per digit are described.

United States Patent Alfred D. Scarbrough lnventor Northridge, Calll. Appl. No. 5,737 Filed Jan. 26, 1970 Patented Nov. 23, 1971 Assignee The Bunker-Balm Corporation Oak Brook, lll. Continuation-impart of application Ser. No. 160, Jan. 2, 1970.

SELF-ENCODING KEYBOARD EMPLOYING EDDY CURRENT SHORTING 26 Claims, 19 Drawing Figs.

U.S. Cl 340/365, 235/ l 45 03k 13/00 Field of Search 340/365,

174 AB, 174 EC; 179/90 K; 235/145, 146

[56] References Cited UNITED STATES PATENTS 3,160,875 l2/l964 Bernard 340/365 3,210,734 10/1965 Andrews et al.. 340/365 3,495,236 2/ I970 Mathamel 340/365 Primary Examiner-Richard Murray Assistant Examiner-Peter M. Pecori Attorney-Frederick M. Arbuckle ABSTRACT: A self-encoding keyboard which employs eddy current shorting effects for generating coded digital electrical signals representative of actuated keys. Each key includes a metal element which upon actuation of the key is brought into close proximity to a corresponding group of stacked printed circuit windings so as to produce an eddy current shorting effect which is detected and used to produce a group of coded digital output signals uniquely representative of the actuated key. Winding encoding arrangements employing two windings per binary digit as well as a single winding per digit are described.

SELF-ENCODING KEYBOARD EMPLOYING EDDY CURRENT SHORTING CROSS-REFERENCE TO RELATED PATENT APPLICATION This application is a continuation-in-part of the copending commonly assigned patent application for "Self-Encloding Keyboard Employing Eddy Current Shorting," Ser. No. I60, filed on Jan. 2, 1970.

BACKGROUND OF THE INVENTION This invention relates generally to keyboards and the like, and to means and methods for providing electrical signals representative of actuated keys.

It will be recognized that various approaches are known for designing keyboard apparatus. In one conventional approach, a keyboard construction is provided which operates based on magnetic coupling principles for producing coded electrical output signals representative of actuated keys. While such a magnetic keyboard has the advantage of eliminating the need for mechanical switching means, known structures have the disadvantage of requiringrelatively expensive and/or complex structures and circuit arrangements.

BRIEF DESCRIPTION OF THE PRESENT INVENTION In accordance with the present invention, a novel keyboard is provided which operates on magnetic coupling principles, but yet is capable of being constructed in a remarkably simple and inexpensive manner. This is accomplished by employing eddy current shorting principles in a novel manner which permits generating electrical output signals representative of actuated keys using noncritical, simply providable key-operating members, and without the need of providing special magnetic elements for the keys. The present invention also provides novel means, including a unique two winding per binary digit encoding arrangement, for employing eddy current shorting principles for generating digitally coded output signals representative of actuated keys.

The specific nature of the invention as well as other objects, features, advantages and uses thereof will become apparent from the following description of a typical exemplary embodiment of the invention taken in conjunction with the accompanying drawings in which: I

FIG. 1 is a fragmentary top view of a keyboard in accordance with the invention;

FIG. 2 is a side view ofthe keyboard of FIG. 1;

FIG. 3 is a fragmentary view illustrating a stamping of sheet spring stock which when bent along the indicated dashed lines forms the operating members for one of the rows of keys for the keyboard of FIGS. 1 and 2;

FIG. 4 is a side, partially cross-sectional view illustrating the resulting shape of each key-operating member after bending of the stamping of FIG. 3;

FIGS. 5-10 are schematic views illustrating the construction and arrangement of the encoding wafers of a typical keyboard encoding means in accordance with the invention;

FIG. 11 is a fragmentary cross-sectional view showing how the encoding wafers of FIGS. 5-10 may be stacked to form an encoding means, and also showing the resulting position of an eddy current shorting element when its respective key is depressed;

FIG. 12 is a schematic plan view illustrating a typical binary encoding which may be provided for the 16 keys of a keyboard using the encoding wafers illustrated in FIGS. 5-9; and

FIGS. 13-18 are schematic diagrams illustrating a further embodiment of the invention which employs a two winding per binary digit encoding arrangement.

FIG. 19 is a schematic electrical circuit diagram illustrating a possible modification of the invention.

Like characters refer to like elements throughout the drawings.

Referring to FIGS. 1 and 2, illustrated therein is a fragmentary portion of a typical keyboard in accordance with the invention. It will become apparent from the description to be provided herein that the present invention is applicable to a wide variety of keyboard arrangements with differing numbers of keys. I

The basic construction and arrangement of the keyboard of FIGS. 1 and 2 will best be understood from a consideration of FIGS. 3 and 4. FIG. 3 illustrates a stamping 18 of sheet spring stock, preferably of beryllium copper, from which the operating members 19 (FIGS. 2 and 4) of a typical row may be formed, there being one such stamping 18 for each row of keys of the keyboard. The stamping 18 of FIG. 3 comprises a generally rectangular portion 16 having perpendicularly depending elongated spaced-parallel portions 17 which when bent along the indicated dashed lines form the commonly connected key-operating members 19 of a row, as illustrated by the side view of FIG. 4.

It will be seen that each operating member 19 comprises an upper portion 190 (FIG. 4) which receives an actuating cap 20 (FIGS. 1 and 2) in a conventional manner, a lower portion 1% (FIGS. 2 and 4) having a generally right-angular shape with a horizontal element 19b which is used to provide eddy current shorting as will hereinafter be explained, and an elongated horizontal central portion 19c (FIGS. 1,2, and 4) for coupling to the common portion 16 (FIGS. 1-4) of its respective row. The thus formed rows of operating members 19 are assembled as shown in FIGS. 2 and 3 with their supporting portions 16 rigidly afiixed to respective steps of a keyboard base 25 by respective rigid plates 24 (FIGS. 1 and 2) disposed thereover and secured by screws 22 (FIG. 2) passing through appropriately located aligned holes 23, 26 and 27 respectively provided in the portions 16, the plates 24 and the base 25.

Next to be considered is the manner in which the invention may typically employ eddy current shorting principles for generating a unique group of digitally coded output signals in response to the actuation of each key of a keyboard. As will be seen from FIG. 2, an encoding means 30is provided beneath the keys 15. when a key 15 is actuated, such as by manual depression, the horizontal element 19b of its respective operating member 19 is moved downwardly into a position of close proximity to a respective area of the top surface of the encoding means 30, there being a like but different respective area for each key of the keyboard. Because the operating members 19 are formed from spring sheet stock, such as beryllium copper, it will be understood that a depressed key will spring back to its original position when the depressing force is removed.

FIGS. 5-9 illustrate the nature of five encoding wafers 31-55 which may be stacked to form an encoding means 30 (FIG. 2) for a keyboard having, for example, 16 keys. Each of the encoding wafers 31-35 may typically comprise a printed circuit board formed of an insulative substrate 39 having a unique predetermined conductive pattern of 16 interconnected windings 31a-35a respectively provided thereon. The windings on all of the wafers have the same respective positions, and each of the 16 windings on a wafer corresponds to a respective one of the 16 keys of the keyboard. Although the windings on the encoding wafers 31-35 of FIGS. 5-9 are all illustrated as having only a single turn, it is to be understood that multiple-tum windings may also be employed. It is also to be understood that other encoding arrangements may be employed for which a plurality of windings may be provided on each wafer for each key of the keyboard as will be considered later on herein in connection with FIGS. 13-18.

As shown in FIG. 11, the encoding wafers 31-35 are stacked with their respective like-positioned windings aligned and with a metal shielding wafer 37 (FIG. 10) preferably interposed between each adjacent pair for shielding purposes. Each metal shielding wafer 37 has openings 37a concentric with and of greater size than the windings on the wafers so as to permit magnetic coupling only among each group of vertically aligned windings. FIG. 11 also illustrates the position of the eddy current shorting element 19b of a depressed key relative to a respective group of vertically aligned windings when the key is depressed. The thicknesses of the wafers in FIG. 11 are exaggerated for greater clarity of illustration. The

encoding means 30 is also provided with a top layer 40 of 5 suitable insulative material so as to protect the topmost encoding wafer from possible shorting.

Next to be considered is the specific manner in which encoding is typically provided in response to key actuation for the exemplary embodiment of the invention being described herein. Basically, encoding is obtained as a function of the relative polarities provided for the 16 windings on each of the encoding wafers 31-35, the arrows on the windings indicating their respective polarities. The windings 31a of the wafer 31 (FIG. 5) serve as drive windings, while the windings 32a-35a on the respective wafers 32-35 (FIGS. 6-9) serve as sense windings. The drive windings 31a of the wafer 31 are connected to each other and to a continuously running pulse generator 44 and line matching impedance 46 so that each drive winding has the same polarity, whereby to cause each drive winding to generate a like polarity magnetic field in response to each pulse from the pulse generator 44. The respective sense windings 32a-35a on each of the other wafers 32-35 are connected to each other and to a respective wafersensing means 47 and line matching impedance 46 so that a unique combination of sense winding polarities is provided for each wafer.

At this point in the description it may be noted that conventional techniques may be employed for connecting the windings of the wafer 31 to the pulse generator 44 and line matching impedance 46 (FIG. 5), and from the windings of the wafers 32-35 to the respective sensing means and line matching impedances 46 (FIGS. 6-9). Conventional techniques may also be employed for providing the jumper 38 shown on the wafers 32-35 for connecting overlapping portions of the interconnection circuitry.

Continuing with the description of the encoding means, it will be evident from FIGS. 6-9 that half of the sense windings on each of the wafers 32-35 have one polarity and the other half the opposite polarity. Accordingly, when no key of the keyboard is actuated, a pulse applied to the drive windings of the wafer 31 (FIG. 5) from the pulse generator 44 will cause an equal number of like-amplitude positive and negative pulses to be induced in the sense windings of each wafer so that essentially no resultant signal is coupled to any of the wafersensing means 47. It will be understood that the particular interconnection arrangements shown for connecting the windings of the wafers 31-35 have been chosen to reduce noise and minimize undesired couplings. It will also be understood that the sensing means 47 may be of conventional form, and preferably includes threshold means for rejecting signals having amplitudes below a predetermined threshold level so as to reject unwanted noise.

With reference now to FIGS. 2 and 11, it will be understood that, when a key is depressed, the eddy current shorting element 19b thereof is brought into close proximity to a respective group of vertically aligned drive and sense windings on the wafers of the encoding means 30. The relative dimensions of the element 19b and its respective windings is chosen to be such that sufficient eddy current shorting is produced as a result of the proximity of the element 19b so as to significantly reduce the amplitude of the pulses induced in the respective sense windings from the respective drive winding in response to a pulse from the pulse generator 44. As a result, equal numbers of positive and negative pulses will no longer be induced in the sense windings of each wafer, as occurred when no key was actuated. Instead, a resultant pulse will be coupled to each wafer-sensing means 47 having a polarity determined by the polarity of the respective wafer-sense winding. The relative polarities provided for the sense windings on each of the wafers 32-35 are chosen so that the resulting pulses applied to the wafer-sensing means 47 constitute a pulse combination uniquely representative of the depressed key,

and which pulse combination can be sensed in a conventional manner and then fed to appropriate utilization means.

The particular exemplary encoding scheme employed in the embodiment of the invention is a straightforward binary system, as will shortly become apparent. For the purposes of this discussion, it will be assumed that a sense winding having a clockwise polarity will, when its respective key is actuated, cause a resultant positive pulse to be coupled to its respective wafer-sensing means 47 in response to each pulse from the pulse generator 44, or a resultant negative pulse if the sense winding has a counterclockwise polarity. It will arbitrarily be assumed that such a resultant positive pulse coupled to a sensing means 47 corresponds to a binary l and that such a resultant negative pulse coupled to a sensing means 47 corresponds to a binary 0." I

It will be understood from a study of the polarities of the sense windings on the wafers 32-35 of FIGS. 6-9, that, using the above assumptions, each of the l6 keys of the keyboard will upon actuation produce a unique four-digit binary number as indicated on each key in FIG. 12. The binary digits of each such four-digit number are determined by the polarities of the respective sense windings, the least significant binary digit is determined by the polarity of the respective sense winding of the wafer 32, the most significant binary digit is determined by the polarity of the respective sense winding of the wafer 35, and the two intermediate binary digits proceeding from the least to the most significant digits are determined by the polarities of the respective sense windings of the wafers 33 and 34, respectively.

An example of typical operation will now be provided. It will be remembered that, when no key of the keyboard is depressed, substantially no resultant signal is coupled to any of the wafer sensing means 47 (FIGS. 4-9) in response to pulses from the pulse generator 44, because equal numbers of positive and negative pulses are induced into the sense windings of each of the wafers 32-35 from the respective drive windings of the wafer 31 (FIG. 5). For the purposes of this example, it will be assumed that the key in the extreme lower right position of the keyboard illustrated in FIG. 12 is actuated. It will be seen from FIG. 12 that this key corresponds to the binary number l 100. Actuation of this key causes the respective eddy current shorting element 19b thereof(FIGS. 2 and 11) to be brought into close proximity to the surface 40 of the encoding means 30 over the corresponding extreme lower right drive and sense windings of the encoding wafers.

As a result, each pulse from the pulse generator 44 (FIG. 5) will cause a resultant pulse to be coupled to each wafersensing means 47 (FIGS. 6-9) having a polarity determined by the polarity of the sense winding in the extreme lower right position of each wafer. It will be noted from FIGS. 6-9 that the extreme lower right sense windings of the wafers 32 and 33 are counterclockwise, while those of the wafers 34 and 35 are clockwise. Consequently, in accordance with the previous assumptions made herein, such polarities will cause positive and negative pulses to be applied to the wafer-sensing means 47 which correspond to the binary number l 100, as illustrated on the extreme lower right key in FIG. 12.

Referring now to FIGS. 13-18, illustrated therein are printed circuit board encoding wafers 131-135 (FIGS. 13-17 and a typical metal shielding wafer 137 (FIG. 18) which are stacked in the manner illustrated in FIG. 11 whereby to provide a two winding per binary digit encoding means 30 (FIG. 2) which has the important advantage of exhibiting a greatly improved signal-to-noise ratio.

For ease of understanding and identification, FIGS. 13-18 have been made to respectively correspond to FIGS. 5-9. Similar functioning elements in FIGS. 13-18 are given the same number designation as in FIGS. 5-10, except increased by I00.

To further aid in understanding the two winding binary digit encoding arrangement of FIGS. 13-17, its winding polarities and interconnections have been chosen so that the wafersensing means 147 will provide output signals in response to key actuation corresponding to the same unique binary numbers indicated in FIG. 12 for the previously described single winding per binary digit encoding arrangement of FIGS. 5-9.

It will thus be understood from a comparison of FIGS. 5-9 and 13-17 that the two winding per binary digit encoding arrangement illustrated in FIGS. 13-17 adds a noise cancelling winding adjacent to each of the single windings provided in the previously described single winding per binary digit encoding arrangement illustrated in FIGS. 5-9, as illustrated for the typical pair of windings designated by the letters A and B in FIGS. 13-17. In the particular exemplary embodiment of the two winding per binary digit encoding arrangement being considered herein, the respective eddy current shorting elements 19c (FIGS. 2 and 4) continue to cooperate with their respective first windings in the manner previously described for the single winding embodiment of FIGS. 5-9, while having relatively negligible effect on the noise cancelling windings. It will be understood from the description herein that the invention is not limited to such operation.

One way for providing for noise cancellation in the exemplary two winding per digit embodiment being described is to provide a balanced pulse generator 144 (FIG. 13) for providing like pulses to the pairs ofdrive windings 131, and balanced sensing means 147 (FIGS. 14-17) for receiving signals from the pairs of sense windings in an appropriate polarity sense, so as to achieve noise cancellation. In other words, the polarities of the pairs of sense windings on each wafer and their interconnections to each other and to their respective wafersensing means are chose so that, when no key is actuated, the signals coupled from each sense winding pair to their respective sensing means 147 are equal and opposite so as to thereby cancel one another, whereby no resultant signal is coupled to the sensing means 147. When a key 15 (FIGS. 1 and 2) is actuated, this cancellation will no longer occur for the respective winding pairs corresponding to the actuated key, because of the eddy current shorting produced on one winding of each such pair. Thus, when a key is actuated, resultant signals will be coupled to the sensing means 147 having polarities determined by the polarities of the winding pairs corresponding to the actuated key. As mentioned previously, the polarities and connections of the windings on the wafers of FIGS. 13-18 are chosen to provide the same unique binary numbers indicated for the keys 15 in FIG. 12. It should now be evident that the provision and connection of the noise cancellation windings as described above and illustrated in FIGS. 13-18 results in a high degree of common mode noise cancellation at the sensing means 147 so as to permit obtaining a very much higher signal-to-no se ratio than would otherwise be possible.

Although the invention has been described in connection with certain particular exemplary embodiments thereof, it is to be understood that the invention is subject to a wide range of variations, modifications and extensions in construction, arrangement, operation and use without departing from the spirit of the invention.

For example, the invention can be extended to provide ad ditional infonnation, such as an indication that more than one key has been simultaneously depressed. This condition can be detected by including conventional means in the sensing means for monitoring the amplitudes of the pulses coupled thereto from the sense windings of the wafers, since these pulse amplitudes contaimthe necessary information to make such a determination. For example, the fact that two keys are simultaneously depressed can readily be detected since, in such a situation, at least one sensing means will receive substantially no resultant signal in response to pulses from the pulse generator.

Also, the manner in which the encoding wafers are employed for encoding is subject to many variations. For example, FIG. 19 illustrates a modified arrangement which may be employed with either the single or two winding per binary digit encoding arrangements. In the embodiment of FIG. 19, the windings of the wafers 32-35 (FIGS. 6-9) or 132-135 (FIGS. 13-17) are used as drive windings instead of as sense windings. while the windings of the wafer 31 (FIG. 5) or 131 (FIG. 14) are used as sense windings instead of as drive windings. In such a modification, a single sensing means 47 or 147 is provided for the windings of the wafer 31 or 131, and the pulse generator 44 or 144 is now employed for use with the windings of the wafers 32-35 or 132-135 to sequentially apply pulses thereto under the control of conventional switch logic 51. The switch logic 51 causes pulses from the pulse generator 44 or 144 to be sequentially applied to the windings of the wafers 32-35 or 132-135 so that only one wafer receives a pulse at any one time.

The operation of the modified embodiment of FIG. 13 will accordingly be understood to be such that, when no key is actuated, the application of a pulse from the pulse generator to the windings of any one of the wafers 32-35 or 132-135 causes substantially no resultant pulse to be coupled to the sensing means 47 or 147. However, when a key is actuated, the eddy current shorting produced on the respective windings of the wafers will cause a resultant pulse to be coupled to the sensing means in response to each pulse of the pulse generator, the polarity of each such resultant pulse being determined by the polarity of the respective winding corresponding to the depressed key on the wafer to which the generator pulse is applied. It will thus be evident that, for the modification of FIG. 19, the actuation of a key will cause resultant pulses to be coupled to the sensing means 47 or 147 corresponding to the same unique four-digit binary number indicated in FIG. 12, except that the resultant pulses are now sequentially produced, rather than simultaneously as in the previously described embodiment.

It will also be evident that, although the exemplary encoding means considered herein and the keyboard shown in FIG. 19 correspond to a rectangular row-column arrangement of the keys, any other suitable keyboard arrangement may also be employed, such as the staggered arrangement suggested in FIG. 1.

The above examples of possible modifications and variations are by no means exhaustive and the present invention is to be considered as including all possible modifications and variations coming within the scope of the invention as defined in the appended claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In apparatus for encoding information,

a plurality of actuatable keys,

a plurality of winding means respectively corresponding to said keys, eddy current shorting means responsive to actuation of a key for causing eddy current shorting to occur with respect to the winding means corresponding thereto,

means responsive to the occurrence of eddy current shorting in a winding means for producing an electrical output uniquely representative of the key corresponding thereto, and

noise cancelling means cooperating with the means responsive to the occurrence of eddy current shorting for achieving a higher signal-to-noise ratio.

2. The invention in accordance with claim 1,

wherein said eddy current shorting means includes an eddy current shorting element for each key operable to be moved into proximity to a respective winding means when a key is actuated.

3. The invention in accordance with claims 2,

wherein said noise cancelling means includes a noise cancelling winding means located adjacent to each of said plurality of winding means.

4. The invention in accordance with claim 3,

wherein each noise cancelling winding means is relatively unafiected by the operation of the corresponding eddy current shorting means.

5. The invention in accordance with claim 2,

wherein each eddy current shorting element includes a metal member mechanically coupled to its respective key.

6. The invention in accordance with claim 2,

wherein each of said plurality of winding means includes a corresponding plurality of windings.

7. The invention in accordance with claim 6,

wherein said plurality of winding means are disposed in a plurality of adjacent planes with the plurality of windings corresponding to each winding means being distributed among said planes and located in close proximity to one another.

8. The invention in accordance with claim 6,

wherein said apparatus includes driving means and sensing means, and

wherein at least one of each corresponding plurality of windings is a drive winding coupled to said driving means and at least one other one is a sense winding coupled to said sensing means.

9. The invention in accordance with claim 8,

wherein noise cancelling windings are additionally provided and coupled to said driving means and said sensing means so as to obtain common mode noise cancellation.

10. The invention in accordance with claim 9,

wherein said noise cancelling windings are provided by providing an additional plurality of windings adjacent each plurality of windings corresponding to a winding means.

11. The invention in accordance with claim 8,

wherein the windings of the plurality of winding means are interconnected so as to form at least one group of interconnected drive windings coupled to said driving means and at least one group of interconnected sense windings coupled to said sensing means.

12. The invention in accordance with claim 11,

wherein the windings of said plurality of winding means are disposed in a plurality of adjacent planes with each group being disposed in one of said planes and with corresponding windings having like relative positions.

13. The invention in accordance with claim 12,

wherein each group of interconnected windings additionally includes a respective noise cancelling winding for each winding of the group. i

14. The invention in accordance with claim 13,

wherein each noise cancelling sense winding is located and coupled to said sensing means so as to cancel out signals induced in its respective sense winding when its respective key is not actuated while permitting coupling of a signal to said sensing means when its respective key is actuated.

15. The invention in accordance with claim 14,

wherein the construction and arrangement of each noise cancelling winding is such that it experiences a negligible eddy current shorting effect when its respective key is actuated.

16. The invention in accordance with claim 15,

wherein said apparatus includes driving means and sensing means, and

wherein at least one of each corresponding plurality of windings is a drive winding coupled to said driving means and at least one other one is a sense winding coupled to said sensing means,

17. The invention in-accordance with claim 16,

wherein the windings of the plurality of winding means are interconnected so as to form at least one group of interconnected drive windings coupled to said driving means and at least one group of interconnected sense windings coupled to said sensing means.

18. The invention in accordance with claim 12,

wherein each plane is comprised of a sheet of insulative material having its respective group of interconnected windings provided thereon.

19. The invention in accordance with claim 12,

wherein each group of interconnected drive windings has its drive windings interconnected so that each drive winding has the same relative polarity, and wherein each group of interconnected sense windings has its sense windings interconnected so that half of its sense windings have one relative polarity and the other half the opposite relative polarity.

20. The invention in accordance with claim 19,

wherein the windings in each group are connected in series.

21. The invention in accordance with claim 11,

wherein the windings in each group and their interconnections are chosen so that the actuation of a key results in a unique combination of signals being coupled to said sensing means.

22. The invention in accordance with claim 21,

wherein a plurality of groups of interconnected sense windings are provided coupled to said sensing means, and

wherein said sensing means includes a sensing means for each group of sense windings.

23. The invention in accordance with claim 21,

wherein a plurality of groups of interconnected drive windings are provided, and

wherein switch logic means are also provided for sequentially coupling said driving means to the groups of interconnected drive windings.

24. In apparatus for encoding information,

a base structure,

a plurality of rows of keys, each row comprising an integral sheet of spring metal stock shaped so as to form a planar supporting portion by which the row is secured to said base structure, said supporting portion having elongated spaced parallel key-operating members depending substantially perpendicularly therefrom and each being individually di'splaceable in a direction substantially perpendicular to the plane of said supporting portion,

each key-operating member including a cap receiving portion at one end and an eddy current shorting element at the other end,

encoding means provided adjacent the eddy current shorting elements of said rows of keys so that the actuation of a key causes its respective key-operating member to move toward said encoding means to bring its respective eddy current shorting element into proximity to a unique respective portion of said encoding means which in response to this proximity produces an electrical output signal uniquely representative of the actuated key, and

a noise cancelling winding provided adjacent each of the windings corresponding to a key.

25. The invention in accordance with claim 24,

wherein said encoding means comprises a plurality of stacked printed circuit boards each having a unique pattern of interconnected windings provided thereon and driving and sensing means cooperating therewith.

26. A methpd of electrically encoding information entered into a keyboard having a plurality of keys, said method comprising:

providing an eddy current shorting element coupled to each key and movable in response to actuation thereof,

providing a plurality of close proximity windings corresponding to each key of the keyboard and located so that the actuation of the corresponding key causes the respective eddy current shorting element to move into proximity thereto, each plurality of close proximity windings including at least one drive winding and one sense winding,

additionally providing a noise cancelling winding adjacent each of the windings corresponding to a key,

electrically energizing the drive windings of the keys, and

sensing the reduced coupling occurring between the drive and sense windings corresponding to an actuated key because of the proximity of the respective eddy current shorting element for producing in response thereto an electrical output uniquely representative of the actuated key. 

1. In apparatus for encoding information, a plurality of actuatable keys, a plurality of winding means respectively corresponding to said keys, eddy current shorting means responsive to actuation of a key for causing eddy current shorting to occur with respect to the winding means corresponding thereto, means responsive to the occurrence of eddy current shorting in a winding means for producing an electrical output uniquely representative of the key corresponding thereto, and noise cancelling means cooperating with the means responsive to the occurrence of eddy current shorting for achieving a higher signal-to-noise ratio.
 2. The invention in accordance with claim 1, wherein said eddy current shorting means includes an eddy current shorting element for each key operable to be moved into proximity to a respective winding means when a key is actuated.
 3. The invention in accordance with claims 2, wherein said noise cancelling means includes a noise cancelling winding means located adjacent to each of said plurality of winding means.
 4. The invention in accordance with claim 3, wherein each noise cancelling winding means is relatively unaffected by the operation of the corresponding eddy current shorting means.
 5. The invention in accordance with claim 2, wherein each eddy current shorting element includes a metal member mechanically coupled to its respective key.
 6. The invention in accordance with claim 2, wherein each of said plurality of winding means includes a corresponding plurality of windings.
 7. The invention in accordance with claim 6, wherein said plurality of winding means are disposed in a plurality of adjacent planes with the plurality of windings corresponding to each winding means being distributed among said planes and located in close proximity to one another.
 8. The invention in accordance with claim 6, wherein said apparatus includes driving means and sensing means, and wherein at least one of each corresponding plurality of windings is a drive winding coupled to said driving means and at least one other one is a sense winding coupled to said sensing means.
 9. The invention in accordance with claim 8, wherein noise cancelling windings are additionally provided and coupled to said driving means and said sensing means so as to obtain common mode noise cancellation.
 10. The invention in accordance with claim 9, wherein said noise cancelling windings are provided by providing an additional plurality of windings adjacent each plurality of windings corresponding to a winding means.
 11. The invention in accordance with claim 8, wherein the windings of the plurality of winding means are interconnected so as to form at least one group of interconnected drive windings coupled to said driving means and at least one group of interconnected sense windings coupled to said sensing means.
 12. The invention in accordance with claim 11, wherein the windings of said plurality of winding means are disposed in a plurality of adjacent planes with each group being disposed in one of said planes and with corresponding windings having like relative positions.
 13. The invention in accordance with claim 12, wherein each group of inteRconnected windings additionally includes a respective noise cancelling winding for each winding of the group.
 14. The invention in accordance with claim 13, wherein each noise cancelling sense winding is located and coupled to said sensing means so as to cancel out signals induced in its respective sense winding when its respective key is not actuated while permitting coupling of a signal to said sensing means when its respective key is actuated.
 15. The invention in accordance with claim 14, wherein the construction and arrangement of each noise cancelling winding is such that it experiences a negligible eddy current shorting effect when its respective key is actuated.
 16. The invention in accordance with claim 15, wherein said apparatus includes driving means and sensing means, and wherein at least one of each corresponding plurality of windings is a drive winding coupled to said driving means and at least one other one is a sense winding coupled to said sensing means.
 17. The invention in accordance with claim 16, wherein the windings of the plurality of winding means are interconnected so as to form at least one group of interconnected drive windings coupled to said driving means and at least one group of interconnected sense windings coupled to said sensing means.
 18. The invention in accordance with claim 12, wherein each plane is comprised of a sheet of insulative material having its respective group of interconnected windings provided thereon.
 19. The invention in accordance with claim 12, wherein each group of interconnected drive windings has its drive windings interconnected so that each drive winding has the same relative polarity, and wherein each group of interconnected sense windings has its sense windings interconnected so that half of its sense windings have one relative polarity and the other half the opposite relative polarity.
 20. The invention in accordance with claim 19, wherein the windings in each group are connected in series.
 21. The invention in accordance with claim 11, wherein the windings in each group and their interconnections are chosen so that the actuation of a key results in a unique combination of signals being coupled to said sensing means.
 22. The invention in accordance with claim 21, wherein a plurality of groups of interconnected sense windings are provided coupled to said sensing means, and wherein said sensing means includes a sensing means for each group of sense windings.
 23. The invention in accordance with claim 21, wherein a plurality of groups of interconnected drive windings are provided, and wherein switch logic means are also provided for sequentially coupling said driving means to the groups of interconnected drive windings.
 24. In apparatus for encoding information, a base structure, a plurality of rows of keys, each row comprising an integral sheet of spring metal stock shaped so as to form a planar supporting portion by which the row is secured to said base structure, said supporting portion having elongated spaced parallel key-operating members depending substantially perpendicularly therefrom and each being individually displaceable in a direction substantially perpendicular to the plane of said supporting portion, each key-operating member including a cap receiving portion at one end and an eddy current shorting element at the other end, encoding means provided adjacent the eddy current shorting elements of said rows of keys so that the actuation of a key causes its respective key-operating member to move toward said encoding means to bring its respective eddy current shorting element into proximity to a unique respective portion of said encoding means which in response to this proximity produces an electrical output signal uniquely representative of the actuated key, and a noise cancelling winding provided adjacent each of the windings corresponding to a key.
 25. The inveNtion in accordance with claim 24, wherein said encoding means comprises a plurality of stacked printed circuit boards each having a unique pattern of interconnected windings provided thereon and driving and sensing means cooperating therewith.
 26. A method of electrically encoding information entered into a keyboard having a plurality of keys, said method comprising: providing an eddy current shorting element coupled to each key and movable in response to actuation thereof, providing a plurality of close proximity windings corresponding to each key of the keyboard and located so that the actuation of the corresponding key causes the respective eddy current shorting element to move into proximity thereto, each plurality of close proximity windings including at least one drive winding and one sense winding, additionally providing a noise cancelling winding adjacent each of the windings corresponding to a key, electrically energizing the drive windings of the keys, and sensing the reduced coupling occurring between the drive and sense windings corresponding to an actuated key because of the proximity of the respective eddy current shorting element for producing in response thereto an electrical output uniquely representative of the actuated key. 